Catheters or probes are used in a number of medical and related applications. For example, a catheter comprising an elongated, flexible, hollow tube may be inserted into a patient's urethral canal to permit withdrawal of fluids from the bladder. Such catheters are typically referred to as urinary drainage catheters, or simply urinary catheters, and are usually inserted into the bladder by way of the urethra.
It has been found that typical urinary catheters, even if sterile when inserted into a patient, tend to contribute to bladder infections Treatment of such infections often involves the use of heavy medication and may lengthen the catheterized patient's hospital stay. It is believed that the insertion of the catheter through the urethral canal into the bladder dislodges or otherwise attracts infectious material, (i.e., pathogens and bacteria which populate the lower urinary tract), due to the frictional forces the catheter exerts on the urethral walls or urethral mucosa resident on the walls. These bacteria are typically present on the male glans or the distal portion of the male's urethra and on the female's urethral meatus. Once dislodged, the infectious material is carried, typically by the leading edge of the catheter, to the internal organ (e.g., bladder), causing infection of the internal organ.
Even if no infectious or pathogenous material is dislodged, the frictional forces exerted on the urethral walls by conventional catheters tend to irritate the urethral mucosa. While the irritation caused by this mechanical trauma exerted during penetration by the catheter is generally temporary, the discomfort experienced by the patient is nonetheless substantial.
These disadvantages are also encountered in other applications in which a probe or catheter is inserted into a body cavity to either drain or inject internal fluids or for other diagnostic procedures. For example, probes used in cystoscopy also may cause attraction of infectious material or irritation to the canal or orifice into which the catheter is inserted.
Other catheters are known which purport to address these problems; for example, the catheters shown in U.S. Pat. No. 3,421,509 issued to Fiore on Dec. 17, 1965; U.S. Pat. No. 3,084,693 issued to Cathcart on Apr. 9, 1963; DE 1958561 issued to American Hospital and published on Jun. 11, 1970; and EP-A-247 559 issued to Sterimed and published on Dec. 2, 1987. While the catheters described in these references purport to address these problems, as will be shown herein, the catheter constructions of these references are medically unacceptable and, in practice, are inferior in performance to or considerably more complex than the catheter of the present invention. Some of the known catheter constructions simply do not work at all.
There thus exists a long-felt need to ameliorate the disadvantages occasioned by use of known medical probes. There is a particular need for a urinary catheter that does not cause infectious material to be carried or otherwise passed to the bladder.